In some special cases, when an artificial component is needed to be fitted at a knee joint of human body, the femoral condyle must be cut and shaped to make the femoral condyle to be a specific shape, in order to co-operate with a corresponding artificial component.
At present, in the operation course of Total Knee Arthroplasty (TKA), it tends to take a very long time for an orthopaedic surgeon to assure that the knee joint is well fitted and balanced. A proper ligament tension can be achieved when the balanced knee joint has a desired angle between the mechanical axis and the anatomic axis of the knee. The proper ligament tension is very important for the perfect motion of the knee joint. Thus, a more natural and effective artificial component of the knee joint and the wear resistance characteristics of the artificial component can be provided. The correct dimensions of the artificial component are also a very important factor, which will bring the operation into success or failure. If a wrong component is selected, or some dimension errors of the artificial component are formed, the associated soft tissue may become too tight or too loose, thus arousing a very poor result.
An instrument for orthopaedic surgical operation and a method for using the instrument have been disclosed in a Chinese patent application disclosure CN1132067A. The orthopaedic surgical instrument is used in the total knee arthroplasty to determine the dimension of a femur and a polyethylene component and provide correct alignment indication and help a surgeon to achieve a proper soft tissue balance for the joint. The use of such an orthopaedic surgical instrument can assist a surgeon in selecting dimensions of respective implanted components, determining the cutting amount of a bone on the distal end, providing a correct soft tissue balance and adjusting the instrument for cutting the bone. This known instrument provides a surgeon with several check and verification systems so that the surgeon can check whether the instrument has been correctly adjusted and the joint has been correctly balanced before cutting the femur. This orthopaedic surgical instrument comprises a rotary alignment guide which assists a surgeon to determine correct rotary alignment of the knee joint. The correct rotary alignment of the knee joint is made by referring to standard boundary marks of a femur such as posterior condyle and superior condyle. This rotary alignment guide comprises a groove for guiding a saw blade which is used to remove the posterior condyle of the femur.
In summary, in the traditional art, the cutting operation for the femoral condyle is performed in steps, as shown in FIGS. 1-5. The first step is to perform osteotomy at the proximal tibia. Then, a guide is inserted into the femoral medulla, and the anterior portion of the femoral condyle is cut roughly, through which the rotary position of the femoral component can be determined. Subsequently, the osteotomy at the distal femur is performed to find out the valgus angle and the joint line. Then, the dimensions of the femoral component are calculated. After that, the osteotomy at the anterior and posterior portions of the femoral condyle is performed, and the cruciate ligament and the meniscus are removed. Thereafter, the flexion gap is measured by means of spacers and the correctness of the osteotomy of the tibia is determined, whether the extension gap is correct is determined by extending the knee, and the whole alignment and the balance status of ligaments are measured. If necessary, the osteotomy of the femur is further performed, the distal femur is repaired, the osteotomy in the intercondylar notch of femur is performed, and the osteotomy in a bevel angle is performed. Thereafter, a plug hole for the artificial tibial component is chiseled, and the rotary position of the artificial tibial component is determined. Then, the osteotomy of the patella is performed, a fixing hole for the artificial patellar component is bored, and the motion path of the patella is checked. This conventional method has such disadvantages that a complete match between the shaped surfaces and the artificial component can not be achieved due to cutting for several times, the operation scheme is complex, a lot of operation instruments are needed and the operation time is very long. Such an operation often brings great pains to a patient, or even some accidental cases may occur due to a long time operation. A mismatch between the shaped surfaces and the artificial component may arouse some complications after operation.